Introduction: Textile finishes have long been used to add functional properties to fabrics. These functionalities can be applied to textile substrates in various ways. However, one of the most common approaches is through the use of microcapsules, which provide protection to the encapsulated active compounds against potential adversities. Microcapsules are widely employed in various fields, including textiles, pharmaceuticals, and cosmetics. In the textile sector, they are used in the development of biofunctional textiles, which serve as vehicles for transporting encapsulated actives, allowing them to come into contact with the skin and perform cosmetic or medicinal functions. This study introduces a novel textile finish based on microcapsules containing lemongrass essential oil and salicylic acid, produced via in situ polymerization—a unique combination not previously reported in the literature. Methods: The microcapsules were characterized using scanning electron microscopy (SEM) for morphology, dynamic light scattering (DLS) for particle size, and Fourier-transform infrared spectroscopy (FTIR) for chemical composition. Loading efficiency, thermal stability (via thermogravimetric analysis, TGA), and free formaldehyde detection were assessed to ensure safety compliance. The microcapsules were applied to 100% cotton fabric using the pad-dry technique, with functionalization confirmed by SEM and TGA. Results: SEM revealed an irregular morphology, while DLS indicated an average particle diameter of 1.95 µm. FTIR confirmed the chemical composition, and loading analysis showed 67.90 ± 1.41% lemongrass oil in the core. TGA and formaldehyde detection confirmed compliance with Brazilian Health Regulatory Agency (ANVISA) safety standards. Successful application to cotton fabric was validated by SEM and TGA, demonstrating effective functionalization. Conclusion: The microcapsules produced via in situ polymerization show significant potential for dermocosmetic applications and textile functionalization. This study underscores the innovative potential of combining lemongrass oil and salicylic acid in microcapsules, paving the way for new cosmetotextile products and further exploration in this field.